Fracture Assessments of MarinePipelines and Subsea Components

in Hostile Environments:Critical Concerns and Recent

Developments

Claudio Ruggieri

NAMEFFracture Mechanics and Structural Integrity Research Group

Faculty of EngineeringUniversity of São Paulo - Brazil

Outline

Challenges in Pipeline Safety Standards:Linking Design and Operation

Current Practices and Standards for Defectand Safety Assessments of Pipelines

Innovative Approaches as More Rational andYet More Efficient Integrity AssessmentProcedures for High Perfomance Pipelines

Some Key Critical Concerns Driving FurtherResearch and Development

Going Farther and Deeper......

Increasing Demand forFossil Fuels, IncludingNatural Gas, is PushingOil and Gas Exploitation

and Production toFarther and Deeper

Reservois in Difficult andHostile Environments

Technological Challenges in Pipeline andRiser Design, Installation, Operation,

Inspection and Repair

The Brazilian Pre-Salt Reservoir

The Brazilian Pre-Salt Reservoir

Key Characteristics

More than 2500 m Water Depth. 2000 m Thickness Salt Layer. Gas Pipeline Larger than 18” in

2500 m Long Distance to Shore (300 km) High CO2 Content (8 ~ 20%)

Technological Challenges

Impact on FFS / ECA Procedures and HowDoes It Affect Tolerable Defect Sizes?

Higher Stresses / StrainsDuring Installation Larger Thickness

Including Weldments

Sour Conditions

The “Mysterious” Design Factor....

High Design Stresses Do Not Cause Failure.Damage Does!

The 0.72 Design Factor isa Historical Factor SetMore than 50 Years Ago ! There is No Rational

and Convincing BasisAgainst Increasing It.

Fracture is Always a Concern ....

Failure of Brazilian Pressure Vessel (2000)(Fracture Initiated at Weld Defect)

Conventional Defect Assessments

FFS or ECA Analysis Required

Fundamental Procedure is Based on the “GoodWorkmanship” Philosophy To Ensure That thePipeline/Riser is Free of Fabrication Defects

However, Larger and Often Severe Defects WillInvariably Occur During the Pipeline and RiserService Life.

Two-Parameter Assessment Line Describingthe Interacion of Two Failure Modes:Brittle Fracture and Plastic Collapse

Failure Assessment Diagram Approach

BS 7910 Level 2A

Key Assumption is that the FAD CurveDoes Not Depend on SpecimenGeometry and Strain Hardening:

High Constraint ConditionsLow to Moderate Ductile Material

FAD Approach

More Important, FAD Procedure is aStress-Based Approach !

Current Scenario

New Methods Should be Developed

There is Growing Concern Supported byStrong Field Evidences that Conventional FFSProcedures are not Necessarily Applicable to

Newer Materials and Complex Conditions:X100 Grade Steel, Ultra Deep Waters, Heavy

Thickness Pipes, Sour Environment, etc.

Constraint Effects on Toughness

Flawed Pipes vs. SE(B) Specimens

Cravero and Ruggieri (2007)

Flawed Pipes vs. SE(T) Specimens

Cravero and Ruggieri (2007)

V5

V6

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

V5

V6

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

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SE(T)-P a/W=0,520” Pipe a/t=0,5

by

by

bx

bx

Crack-Tip Plastic Zones

Cravero and Ruggieri (2007)

Constraint Modified FAD Approach

]1[0rQmat

Qmat LKK

]1[)( rQrr LLfK

ToughnessCorrection

Constraint Modified FAD

Strain-Based Analysis Defines a Limit StateCondition in Which Structural Behavior isControlled by Imposed Displacements

Strain-Based Analysis

The Collapse Analysis Built Into FAD ProceduresRelies on Determinig Net Section Yielding in theCrack Ligament

For Higher Grade Steels or Overmatched GirthWelds the Applied Strain Can Be Much Higher

than the Yield Strain

Strain-Based Analysis

When the Material is in the Plastic Range, SmallChanges in Stress Cause Large Changes in Strain

Post-Yield Behavior Does Affect the TolerableDefect Size in a Structural Component

Strain-Based Analysis

After Yielding, the Evolving Near-Tip Stressesand Crack Driving Forces (J, CTOD) StronglyDepend on the Plastic Straining Capacity

Pipe Steels with Lower YT-Ratios (X60) May AllowLarger Defects than Higher YT-Ratios (X100)

Fracture Assessment Using API 579 L2

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1 1.2

rK

rL

API Level 2Limit LoadCorrection

%25.0f

On-Going Research

Development of Test Procedures forConstraint-Designed SE(T) Specimens

FFS Procedures and Biaxial Loading Effectson Reeled Risers

Structural Integrity Assessments of LinedPipes for Reeling

Fatigue and Toughness Behavior of GirthWelds of Lined Pipes under H2 Environment

Constraint-Designed Test Specimens

Pipeline and Riser Installation

Riser Installation by Reeling

FFS Procedures for Reeled Risers

Pipe Reeling Behavior

(From SINTEF Materials Laboratory)

Pipe Reeling Behavior

(From SINTEF Materials Laboratory)

FFS Procedures for Reeled Risers

FFS Procedures for Reeled Risers

Full Compendium of h1 Factors Generated byChiodo & Ruggieri in Polynomial Formfor Easy Manipulation and Codification

Proportionality Between J (CTOD) andApplied Loading is Very Good for High andModerate Hardening (All Crack Config.) andLow Hardening (Shallow Cracks)

Robust Procedure for Most Applications

Application to Pipe Reeling

Estimation of J Based Upon Applied Strain(e.g., DNV-OS-F101)

API Grade 5L X60

J vs. Global Response

Estimation of Maximum CrackDriving Forces in Pipe Reeling

Lined Pipes

Lined pipes consist of a C-Mn pipe which has a layer of CRA incontact with the production fluid and hence, its corrosiveenvironment. The layer of Corrosion Resistant Alloy (CRA) is appliedthrough a mechanical bond between the CRA and the C-Mn pipe.

Key Issues

Wrinkle Formation

Key Issues

Fatigue and Fracture Behavior of Girth WeldsIncluding Hydrogen Assisted Cracking

Summary

Exploitation and Production of Oil and Gas inUltradeep and Hostile Environment Represent Newand Difficult Challenges which Impact Directly theSafety and Integrity Levels of Pipelines and Risers

Application of Current FFS Procedures to NewerMaterials and Complex/Severe Conditions Can Notbe Made by Simple Ad-Hoc Extension ofConventional Engineering Methodologies

Innovative and Yet More Rational and ReliableApproaches Must Be Developed!

Thank you!